Performance Boats Forum banner
1 - 7 of 7 Posts

·
MLC - Mid Life Crisis
Joined
·
1,132 Posts
Discussion Starter · #1 ·
Is there a general rule of thumb for fudging with a head gasket to decrease compression?
 

·
i'm back!!
Joined
·
687 Posts
not really, just like having the piston down in the bore more. Of course by- by quench area, and thats not good for power or detonation.

But yeah if you slapped a .100 thick gasket in there it would drop it quite a bit.
 

·
Registered
Joined
·
2,234 Posts
Jsut do the math...

If you run .125 more in head gasket, the combustion chamber gets that much larger.

The combustion chamber quench area comes into play right away.

Have you considered palying with cam timing also?

How much C/R are we talking about reducing? I have done one point with gaskets, that is about all I felt comfortable with....(went from 11.5:1 to 10.5:1). I used copper gaskets to achieve it.

GT :)hand
 

·
Registered
Joined
·
285 Posts
Is there a general rule of thumb for fudging with a head gasket to decrease compression?
There is a general rule of thumb.... ....but it's wrong!


The amount of static compression change will vary depending on what you're at right now (and the bore to stroke ratio).

For example if you're got a 7.5:1 engine, a few thousands here or there won't change hardly anything. If you're got a 14:1 engine a few thou can make or break you.

You have to know everything to be able to calculate ratios but here's a simple app that will show you what a gasket change will do.

http://users.erols.com/srweiss/calccr.htm
 

·
Resident Ford Nut
Joined
·
10,102 Posts
Is there a general rule of thumb for fudging with a head gasket to decrease compression?

If I recall with my engine with a 66cc chamber (4.6 x 4.25 )the difference from a .040 gasket vs a .050 gasket is .3 points from 12.3 down to 12.0 those are " ball-park" numbers.

Hope it helps you.


Sleeper CP :D
 

·
Premium Member
Joined
·
25,975 Posts

·
Registered
Joined
·
520 Posts
Is there a general rule of thumb for fudging with a head gasket to decrease compression?
More info plz. Why do you want to lower compression? You can get away with much more in our world with an entire lake for a radiator.
But yes you can lower compression with thicker gaskets, not the correct way but it can be done. If you need to cut much you will have to use copper gaskets and you can get them THICK. With more info you will get more accurate and relevent answers.:)bulb
 
1 - 7 of 7 Posts
Top